1. Field of the Invention
The present invention relates to a self-sourcing exercise bike with a linear digital control magnetic resistance braking apparatus. In particular, this invention provides a linear control method to control the change of the magnetic resistance, and the magnetic resistance braking apparatus uses a method of changing inductance and a controlling way thereof to achieve the goal of controlling the variation of the magnetic resistance braking force.
2. Description of the Related Art
The exercise bike is a very popular product for exercise or rehabilitation in the house, gymnasium, and hospital. The resistance or brake apparatus in a self-sourcing exercise bike could be divided into friction brake, oil-pressure brake, electric-magnetic brake and eddy-current brake. To sort them by force, the friction brake and oil-pressure brake are belong to contact force, the electric-magnetic brake and eddy-current brake are belong to surpass-distance force. The brake using the contact force has the shortcomings of wearing due to friction, noise, high temperature and the resistance effect is unstable. So, there are so many researches focusing on the brake using the surpass-distance force.
U.S. Pat. No. 5,042,794 titled “Load Applying Device For An Exercise Bicycle” provides a device for applying a load to a rotating shaft of an exercise bicycle that receives the load. When a user places his feet on the pedals of the exercise bicycle and bends and stretches his legs, the transmission gear of a speed increasing mechanism of the exercise bicycle is rotated by the paddles and thereby, a rotor coupled by a bearing to a fixed main shaft of the load applying device is rotated with respect to the main shaft. The rotor is a magnetic conductor. A magnetic field is provided so that the rotor is passing through a beam-like magnetic flux path produced thereby. When the rotor is rotated, the rotor cuts the magnetic field and thereby produces an induced eddy current, causing an eddy current break effect to the rotor. The drawback is that it needs a man-made effort to adjust the distance of the magnet to control the magnetic braking force.
U.S. Pat. No. 5,234,083 titled “Magnetic Brake” provides a magnetic brake having a combined collar and flywheel with a braking disc and a fan that are all rotatably mounted on a shaft fixed between a pair of frames. The magnetic brake further includes an electro-magnetic coil wound on an electromagnetic ferrite core, a plurality of permanent magnets mounted on an inner surface of the collar, and a stator coil wound on a stator ferrite core disposed in a stator ferrite core seat. An electrical circuit is provided having a rectifying circuit coupled to a first voltage regulating circuit for power the stator winding and the other circuitry. A digital-to-analog converter is included for converting an input digital control signal to an analog control signal. The output of the converter is coupled to a second voltage regulator, the output of which is coupled to a current regulating circuit for driving the stator winding. The drawbacks are that the resistance force of the brake is not enough, and the control and the performance of the resistance force are not good.
U.S. Pat. No. 6,084,325 titled “Brake Device With A Combination Of Power-Generating And Eddy-Current Magnetic Resistance” provides a brake device with a combination of power-generating and eddy-current magnetic resistance having an outer ]-shaped fly wheel fastened on a central axis of a frame and fitted with a permanent magnet on the inner circular edge to form a rotor type, and the fly wheel is connected with a stator core fastened on the frame. Moreover, one end of the central axle is stretching out of the frame and fitted with a belt wheel. The front end the frame is fitted with a brake core adjacent to the outer edge of the flywheel to supply a planned eddy current magnetic resistance to the flywheel. The drawbacks are that the resistance force is still not good, the user cannot change the resistance force linearly with the speed and the presetting force, and it is difficult for the user or the rehabilitant to start up in the initial stage.